Quick acting magnets and electro-magnets



April 24, 1962 Y. PELENC 3,031,602

QUICK ACTING MAGNETS AND ELECTROMAGNETS Filed Jan. 11, 1960 2 Sheets-Sheet 1 o 9 g Y 1 5 i g 5 l3 f e 9 FIG. l0

I I INVENTOR:

- Yves Pelenc ATTORNEYS April 24, 1962 Y. PELENC QUICK ACTING MAGNETS AND ELECTROMAGNETS 2 Sheets-Sheet 2 Filed Jan. 11, 1960 INVENTOR FIG. '3

Yves Pe/enc ATTORNEYS United States Patent QUICK ACTING This invention relates to magnets and electromagnets provided with multiple pole faces arranged so as to provide alternating polarities thereof.

A first object of the invention is to provide a design for such devices which is highly efficient, yet simpler than the designs hitherto achieved.

A second object of the invention is to reduce, for a given surface of the armature, those surfaces of the alternating poles which are located in face-to-face or confronting relationship.

A further object of the invention is, when permanent magnets are involved, to allow a desired controllable variation of the magnetic fiux to be obtained without any danger of demagnetization of the permanent magnets; for example, when the armature is to be released.

I have found that the efficiency of such devices is vastly improved by a design which provides, at the region in which the flux enters the armature, a plurality of effective pole faces of alternate north and south polarities, so that the total area of flux transfer is broken up into multiple regions of individually smaller sectional area. The construction permits also a very low-mass armature, of thin cross-section, to accommodate all of the flux, so that the pulling or holding force is in no way diminished by the small section of the armature. Fast operation and release are thus made possible.

The invention also provides special features to minimize the possibility of demagnetization of any permanent magnet used to establish the holding or pulling force on the armature, especially in cases wherein the fast release of the armature is accomplished by a short, sharp pulse of current through a bucking coil. To this end, two means may be employed; first, the use of a shunt magnetic circuit having an air gap so that it diverts the de-magnetizing flux especially eifectively during the rapid flux changes involved in this kind of quick releasing operation. Second, a shorted winding, or a single heavy shorted turn, as employed in shading coils, is applied to the circuit including such permanent magnet.

Several embodiments of the invention will be described hereinafter, it being understood that the applicant does not wish to limit the generic scope of the invention to or by the specific characteristics of the examples chosen to illustrate the invention.

In the appended drawings:

FIGURE 1 is a perspective view of an electromagnet device according to a first embodiment of the invention.

FIGURE 2 is an elevational schematic view of a modified form of magnet device having a permanent magnet, auxiliary coils being shown in cross-section.

FIGURE 3 is an elevational schematic view of a magnet device according to a further embodiment of the invention.

FIGURE 4 is a perspective view of this last magnet device, with parts shown in phantom lines.

In FIGURE 1, there is shown an electromagnet comprising a magnetic yoke 1 and the arms 2, 3 with the windings of a maintaining coil 4 permanently traversed by a direct current, the north and south poles being designated by N and S. The pole N has three subdivisions having the shape of teeth and flat faces, designated by 5, 6, 7 and the pole S has three similar teeth 8, 9, 10 which are displaced with regard to the teeth of the pole N, so as to allow the interdigitated arrangement as shown.

To minimize the leakage of flux between adjacent confronting flat tooth faces, the edges remote from the main pole structures are preferably cut obliquely as at F.

The bottom edge faces of all of the teeth together form a flat face which is thoroughly machined, the plane of this flat face being parallel to the longitudinal direction of the teeth.

The magnetic flux is closed by the movable magnetic armature 12, the thickness of which may be equal to half the thickness of a tooth; the outer teeth 7 and 8 may, however, have a thickness equal to half the value for the other teeth, without loss of efficiency.

In consideration of the slight thickness of the armature, this latter can be very light and, on the other hand, only small eddy currents can develop in it, even if it is formed from a solid non-laminated material, which gives the armature good mechanical strength.

As an example, it will be noted that the first tests have given, with an armature weighing 65 grams, a bearing or holding force of kilograms, and a response time, for release, of 1W sec.

To obtain this result, on the core 3 there was placed an opposing or bucking coil 13 providing counter ampereturns; that is, a magnetic flux directed opposite to that provided by the coil 4, and a capacitor (not shown) was used to obtain the armature-releasing current impulse through coil 13.

in FIGURE 2, the magnetic flux is obtained by the permanent magnet 39 inserted between the arms 32 and 33 of the magnetic circuit. On the arm 33 is placed the bucking coil 43 providing the counter ampere-turns. The poles are designated by N and S, and they are arrange the same as in FlGURE l, with the interdigitated subdivisions, but only the tooth 33 is visible in full lines in FIGURE 2. The movable armature is indicated by 42.

The main circuit described is shunted by a magnetic circuit forming the poles N, S between which is located an air gap 44.

Finally, around the magnet 36 or elsewhere in the circuit of the arm 32 are placed the windings of the coil 45, short-circuited as by the conductor 46 which connects the terminals of the coil 45. This coil may also comprise a single turn of a heavy conductor.

The device of FIGURE 2 operates as follows:

The shunt circuit at 44 allows the bucking or counterfiux to follow a relatively closed path which does not pass through the magnet 30. It also allows the flux of the magnet 30 to close on a path of relatively low magnetic reluctance, which avoids the demagnetization of the magnet 30 when armature 42 is not in place, and consequently does not then close the magnetic circuit.

The shunt circuit alone, however, cannot efiiciently protect the magnet 30 against demagnetization when a current impulse of very high peak value is sent into the bucking coil 43, as is the case, for instance, when a capacitor discharge is used to create the counter flux which allows the release of the armature 42.

Such an impulse being of very short duration, the magnet 36 is then protected, according to the invention, by means of the short-circuited coil 45, in which any sudden flux variation develops counter ampere-turns which oppose said variation. As a consequence, the flux cannot vary rapidly in the circuit of the magnet 30. The bucking flux, then, flows mainly through the shunt circuit disposed in parallel to the permanent magnet, so that the latter is not subject to demagnetization if, as supposed, the current is maintained in the bucking coil for only a very short time.

According to a further embodiment, shown in FIG- URES 3 and 4, 50 is the permanent magnet around which a short-circuited coil 51 is arranged in order to protect the magnet against demagnetization. The magnetic flux leaving the north pole is transmitted by the yoke 52, 53

I and 54 to the teeth 55. The teeth 61, spacedly interdigited with the teeth 55, are connected to the south pole of the magnet 50 by magnetically permeable cores $6 and 59. The branch 56 constitutes, at the same time, together with the air gaps 57 and 58, the magnetic shunt circuit. Around the branch 59 is disposed the bucking coil 60, while 62 is the magnetic armature, shown in FIG- URE 3 in attracted position and, in FIGURE 4, in re leased position.

It will be recognized that various changes can be made in the disclosed embodiments, by those skilled in the art, without departing from the spirit of the invention in its broader sense. Thus, for example, instead of the solid magnetic structures shown in the drawings for reasons of simplicity of illustration, some or all of such structures can equally well be formed as packs of individual laminations, stamped to provide the general shapes as illustrated. Also, in some cases, a choice can be made as to whether the parts are formed structurally in one piece or are assembled to provide the desired end shape; for example, in FIGURE 1, the teeth through 10 may be considered as integral with their respective pole portions.

Other changes and variations can readily be visualized by those skilled in this art, and the invention is therefore not to be taken as limited by the particular details illustrated and described herein, except as may be required by the scope of the appended claims.

What is claimed is:

1. In a magnetic device, in combination, two parallelepipedal magnetic conductors having two faces perpendicular one with respect to the other and constituting two magnetic poles of opposite polarity, a set of spaced teeth of parallelepipedal shape for each of said conductors, the teeth of each set being applied at one of the faces of the parallelepiped constituting a tooth and on its whole length at one of the said perpendicular faces, the spatial arrangement of the teeth of the first set being such, that the teeth of the second set can protrude into the spaces left between said first teeth leaving between two successive teeth of opposite polarity a gap, the spatial arrangement of the two sets being such that all teeth have one face of the I 3. A magnetic device according to claim 2, wherein a permanent magnet produces the. magnetomotive force, and carries a coil constituted by at least one winding which is short-circuited, to oppose sudden variations of the magnetic flux through the permanentmagnet.

4. In a magnetic device, in combination, two parallelepipedal magnetic conductors of like polarity having two faces parallel to each other and placed face to face, a set of spaced teeth of parallelepipedal shape in magnetic contact with said faces at two opposite faces of the parallelepiped which constitutes each tooth, a third parallelepipedal magnetic conductor of opposite polarity to the polarity of the first two magnetic conductors, a second set of teeth, each tooth thereof being applied edgewise at a face of the parallelepiped constituting the third conductor, the spatial arrangement of the teeth of the first set being such, that the teeth of the second set can protrude into the spaces left between said first teeth leaving between two successive teeth of opposite polarity a gap, the spatial arrangement of the two sets being such that all teeth have one face of theparallelepiped in a common plane.

5. A magnetic device according to claim 4, wherein the two conductors of like polarity are connected by a shunt member including a gap.

6. A magnetic device according to claim 4, wherein the third conductor is disposed perpendicularly to and between the first two conductors, a connecting member connecting the first two conductors, and means to create a magnetomotive force acting between said connecting member and said third conductor.

7. A magnetic device according to claim 6, wherein a permanent magnet is provided to create the magnetornotive force, and including a coil to create reverse ampereturns, and a second coil constituted by at least one winding which is short-circuited and disposed around the .permanent magnet.

References Cited in the file of this patent 'UNITED STATES PATENTS 2,819,430 Sonnemann Jan. 7, 1958 2,888,290 Pierce May 26, 1959 FOREIGN PATENTS 464,049 Canada Mar. 28, 1950 

